Electronically controlled fuel injectors are well known in the art including electronically controlled injectors that may be either hydraulically actuated or mechanically actuated. An electronically controlled fuel injector typically injects fuel into a specific engine cylinder as a function of an injection signal received from an electronic controller. Such control signals comprise waveforms that control injection rate as well as the desired timing and quantity of fuel to be injected into the cylinders.
Due to limitations in the tolerances achievable during the injector manufacturing process, each injector has its own operating nuances (e.g. fuelling and timing variations). Therefore, to achieve the desired control of the performance characteristics of the fuel injectors in a given fuel injection system such as an internal combustion engine, it is advantageous to know the operating characteristics of each injector before it is installed into the fuel injection system.
Each injector is therefore tested prior to installation and a set of trim data (e.g. valve timing offset, nozzle flow offset etc.) that can be used by the ECU to adjust for manufacturing tolerances is produced.
In order to supply the trim data set to the engine system, the trim data may be imprinted or laser etched on the injector surface as a bar-code, dot-code or 2D data matrix (hereinafter referred to as a “code region”). During assembly of the injectors into the engine, the code region may be scanned (by either a human operator or by an automated scanning system) and uploaded into the engine control unit (ECU) where the trim information is used to correct the injections.
Fuel injection equipment (FIE) trim data is traditionally compressed, encrypted and encoded before being incorporated into the code region. This method has tight limitations on the amount of data that can be stored for each injector due to the physical size constraints of the code region. For example, a Data Matrix code is a two-dimensional
matrix barcode consisting of black and white “cells” or modules arranged in either a square or rectangular pattern. The usual data size of such codes is from a few bytes up to approximately 2 kilobytes. Since error correction codes are added to increase symbol strength (so that the code can be read even if partially damaged) this reduces the space available to store trim data.
The resolution of the code region, the space available to etch/imprint the code region and the customer specific requirements relating to the security of the data all limit the amount of data that can be placed within the code region. As a consequence the data is compressed heavily and a reduced number of data points only are included within the code region. For example, an injector may need to be trimmed to the nearest microsecond but the restrictions of the code region may only allow trim data every four microseconds to be stored.
One possible solution to the above issues would be to manufacture components having design tolerances that were extremely accurate. This method would essentially eliminate the need for trim data (and by association the need to monitor trim data) because the components would be essentially identical. However, although such an approach might overcome the above issues it would almost certainly be prohibitively expensive to implement.
An alternative solution would be to integrate an electronic ID chip into the injector such that the trim data may be stored in the ID chip and read by the ECU. This approach however has the disadvantage that additional circuitry often needs to be included within the engine system to allow the ECU to read the trim data from the ID chip.
It is therefore an object of the present invention to provide a method of providing trim data that overcomes or substantially mitigates the above problems.